Srimad Bhagavatam Canto 05, Chapter 18, Text 07

SB 5.18.7

hari-varse capi bhagavan nara-hari-rupenaste; tad-rupa-grahana-nimittam uttaratrabhidhasye; tad dayitam rupam maha-purusa-guna-bhajano maha-bhagavato daitya-danava-kula-tirthikarana-sila-caritah prahlado ’vyavadhanananya-bhakti-yogena saha tad-varsa-purusair upaste idam codaharati.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Sukadeva Gosvami continued: My dear King, Lord Nrsimhadeva resides in the tract of land known as Hari-varsa. In the Seventh Canto of Srimad-Bhagavatam, I shall describe to you how Prahlada Maharaja caused the Lord to assume the form of Nrsimhadeva. Prahlada Maharaja, the topmost devotee of the Lord, is a reservoir of all the good qualities of great personalities. His character and activities have delivered all the fallen members of his demoniac family. Lord Nrsimhadeva is very dear to this exalted personality. Thus
Prahlada Maharaja, along with his servants and all the denizens of Hari-varsa, worships Lord Nrsimhadeva by chanting the following mantra.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Jayadeva Gosvami’s ten prayers worshiping the incarnations of Lord Krsna (Kesava) contain His name in every stanza. For example, kesava dhrta-nara-hari-rupa jaya jagad-isa hare, kesava dhrta-mina-sarira jaya jagad-isa hare, and kesava dhrta-vamana-rupa jaya jagad-isa hare. The word jagad-isa refers to the proprietor of all the universes. His original form is the two-handed form of Lord Krsna, standing with a flute in His hands and engaged in tending the cows. As stated in Brahma-samhita:
cintamani-prakara-sadmasu kalpa-vrksa-
 laksavrtesu surabhir abhipalayantam
 govindam adi-purusam tam aham bhajami
“I worship Govinda, the primeval Lord, the first progenitor, who is tending the cows, yielding all desires, in abodes built with spiritual gems and surrounded by millions of purpose trees. He is always served with great reverence and affection by hundreds and thousands of goddesses of fortune.” From this verse we learn that Govinda, or Krsna, is the adi-purusa (the original person). The Lord has innumerable incarnations, exactly like the innumerable waves of a flowing river, but the original form is Krsna, or Kesava.
Sukadeva Gosvami refers to Nrsimhadeva because of Prahlada Maharaja. Prahlada Maharaja was put into great distress by his powerful father, the demon Hiranyakasipu. Apparently helpless before him, Prahlada Maharaja called on the Lord, who immediately assumed the gigantic form of Nrsimhadeva, half-lion and half-man, to kill the gigantic demon. Although Krsna is the original person, one without a second, He assumes different forms just to satisfy His devotees or to execute a specific purpose. Therefore Jayadeva Gosvami always repeats the name of Kesava, the original Personality of Godhead, in his prayers describing the Lord’s different incarnations for different purposes.
Srimad Bhagavatam Canto 05, Chapter 18, Text 06
Srimad Bhagavatam Canto 05, Chapter 18, Text 08